1. Field of the Invention
The present invention relates to a magnetic head for vertical magnetic recording that is used for writing data on a recording medium by using a vertical magnetic recording system, a method of manufacturing such a magnetic head, and to a head gimbal assembly and a hard disk drive each including the magnetic head for vertical magnetic recording.
2. Description of the Related Art
The recording systems of magnetic read/write device include a longitudinal magnetic recording system wherein signals are magnetized in the direction along the surface of the recording medium (the longitudinal direction) and a vertical (or perpendicular) magnetic recording system wherein signals are magnetized in the direction orthogonal to the surface of the recording medium. It is known that the vertical magnetic recording system is harder to be affected by thermal fluctuation of the recording medium and capable of implementing higher linear recording density, compared to the longitudinal magnetic recording system.
The magnetic heads used for the vertical magnetic recording system include ring heads having a structure similar to the magnetic heads used for the longitudinal magnetic recording system and single-pole heads that apply a magnetic field in the vertical direction to the recording medium by a single main magnetic pole. Where the single-pole head is used, the recording medium typically used is a two-layer vertical recording medium wherein a soft magnetic layer and a magnetic recording layer are stacked on a substrate. A recording system that uses the single-pole head and the two-layer vertical recording medium in combination allows the main pole to generate an intense magnetic field in the vertical direction that exhibits steep changes in the direction in which the recording medium moves. It is therefore expected that this system achieves a high recording sensitivity.
A magnetic head used for a magnetic disk drive such as a hard disk drive is typically provided in a slider. The slider has a medium facing surface that faces toward a recording medium. This medium facing surface has an air-inflow-side end and an air-outflow-side end. The slider slightly flies over the surface of the recording medium by means of the airflow that comes from the air-inflow-side end into the space between the medium facing surface and the recording medium. The magnetic head is typically disposed near the air-outflow-side end of the medium facing surface of the slider.
In the magnetic disk drive that aligns the magnetic head through the use of a rotary actuator, the magnetic head moves on the recording medium along a circular orbit centered on the center of rotation of the rotary actuator. In this case, a tilt called a skew of the magnetic head is generated with respect to the tangent of the circular track, in accordance with the position of the magnetic head across the tracks. The angle of this tilt is called a skew angle. If such a skew angle is generated in the magnetic disk drive, writing on an adjacent track may result.
According to the single-pole head, as disclosed in the Published Unexamined Japanese Patent Application 2002-92821, to prevent writing on an adjacent track when a skew angle is generated, it is often performed that the surface of the main pole exposed from the medium facing surface is made trapezoid-shaped wherein the side located backward in the direction of movement of the recording medium (that is, the side located on the air-inflow-side end of the slider) is smaller than the other side. However, this case has a problem that, if the track width, that is, the width of the main pole taken in the medium facing surface, is reduced to improve the recording density, the main pole is likely to be removed from the underlying layer in the course of the manufacturing process of the magnetic head.
To prevent writing on an adjacent track when a skew angle is generated without causing the above-mentioned problem, it is possible to reduce the thickness of the main pole as the track width is reduced. However, this case has a problem that the area of the surface of the main pole exposed from the medium facing surface is reduced, so that the write field intensity is decreased.
A technique for preventing a decrease in write field intensity disclosed in the Published Unexamined Japanese Patent Application 2002-133610 is that the thickness of the main pole near the medium facing surface is decreased as the distance from the medium facing surface decreases.
Another technique for preventing a decrease in write field intensity disclosed in the Published Unexamined Japanese Patent Application 2002-197615 is that, in a magnetic head incorporating a main pole layer and a yoke layer thicker than the main pole layer, the front-end face of the yoke layer is made to be a sloped surface or a curved surface wherein the distance from the medium facing surface increases as the distance from the main pole layer increases.
According to the magnetic head disclosed in the Published Unexamined Japanese Patent Application 2002-133610, in the neighborhood of the medium facing surface, the surface of the main pole on a side of the air-inflow-side end or the air-outflow-side end is tapered. Consequently, in this magnetic head, in the course of manufacturing process thereof, if the point at which polishing is stopped is shifted when the medium facing surface is formed by polishing, the thickness of the main pole taken in the medium facing surface is varied. This magnetic head therefore has a problem that it is difficult to mass-produce uniform magnetic heads.
According to the magnetic head disclosed in the Published Unexamined Japanese Patent Application 2002-197615, the front-end face of the yoke layer thicker than the main pole layer is disposed near the medium facing surface. As a result, this magnetic head has a problem that writing on an adjacent track is likely to occur, due to the magnetic field generated from the front-end face of the yoke layer, when a skew angle is generated. The magnetic head has another problem that changes in vertical components of the write magnetic field with respect to the direction of movement of the recording medium are made moderate and it is thereby difficult to improve the recording density. Furthermore, according to the magnetic head, the top surface of the yoke layer is flattened and the main pole layer is formed thereon. Consequently, in the magnetic head, in the course of the manufacturing process thereof, if the point at which polishing is stopped is shifted when the top surface of the yoke layer is flattened by polishing, the position of the end of the yoke layer closer to the medium facing surface is varied. This magnetic head therefore has a problem that it is difficult to mass-produce uniform magnetic heads.
According to the magnetic head disclosed in the Published Unexamined Japanese Patent Application 2002-197615, the main pole layer is formed on the yoke layer. In the manufacturing process of this magnetic head the yoke layer and the main pole layer are individually patterned. As a result, misalignment of the yoke layer and the main pole layer of this magnetic head is likely to occur. In the magnetic head, in particular, each of the yoke layer and the main pole layer has a portion near the medium facing surface, the portion having a width smaller than the other portion. Therefore, misalignment of these portions having small widths could cause a reduction in writing characteristics of the magnetic head. In particular, if the track width is reduced down to 0.20 μm or smaller, or 0.15 μm or smaller, a reduction in writing characteristics due to such misalignment is negligible.